Belimumab (Benlysta), a B-cell directed biologic medication, is FDA-approved for the treatment of systemic lupus erythematosus in both children and adults. Real-world effectiveness data in adults shows that patients who start belimumab have fewer lupus flares and need lower steroid doses. However, there is little data on how well belimumab works for children and young adults with lupus. In Aim 1, we will describe characteristics of patients who have received belimumab in the CARRA Registry to better understand current use. In Aim 2, we will compare disease activity, patient reported quality of life, and daily steroid doses at belimumab initiation, to 6 and 12 months after. This will be the first large multicenter study of belimumab in a real-world use setting in children and will provide essential data on belimumab effectiveness and safety.